It is known to use an ammoniacal-ammonium sulfate leach for the recovery of nickel, copper and cobalt values from the oxide ores of nickel and cobalt, which are commonly referred to as lateritic ores. Exemplary of this type of art is U.S. Pat. No. 3,929,468 to Siemens et al, which discloses a selective reduction, oxidizing-ammonia leach process.
It is also known in the prior art to co-extract nickel (II) and copper (II) from an ammoniacal-ammonium sulfate leach liquor produced by the selective reduction, oxidizing-ammonia leach process of U.S. Pat. No. 3,929,468, by use of LIX-64N as the extracting agent, and then to separately recover nickel (II) and copper (II) from the LIX-64N by using spent nickel and copper electrolytes. Furthermore, it is known to recover cobalt (III) from the nickel-copper-free raffinate remaining after nickel and copper co-extraction, by extraction of the raffinate with a .beta.-diketone; to strip the cobalt (III) from the .beta.-diketone along with any zinc (III) present, by using spent cobalt electrolyte; and to separate any zinc (II) with di-(2-ethylhexyl) phosphoric acid. This type of prior art is illustrated by R. E. Siemens and J. D. Corrick, "Process for Recovery of Nickel, Cobalt and Copper from Domestic Laterities", Mining Congress Journal, pages 29-34 (Jan. 1977).
Additionally, the conversion of cobalt (III) to cobalt (II) by contact of the trivalent cobalt with cobalt metal is generally known, as illustrated at column 13, lines 50-57, of U.S. Pat. No. 3,929,468. In this patent, LIX-64N is used to extract the divalent cobalt.
Finally, variation of LIX-64N nickel-loading capacity with ammonia content is described by C. R. Merigold and R. B. Sudderth, "Recovery of Nickel by Liquid Ion Exchange Technology", Ch. in Internat. Symp. on Hydrometallurgy, ed. by D. J. I. Evans, R. S. Shoemaker, pages 552-588 (AIME, N.Y. 1973). This work involves the use of an ammonia-ammonium carbonate system for nickel recovery, and for this system, optimum nickel-loading capacity exists when the ammonia content is high.
This prior art is deficient because these approaches have failed to optimize recovery of the nickel, copper and cobalt metal values. Furthermore, when LIX-64N is used to extract cobalt (II), it is difficult to strip the cobalt (II) from the LIX-64N, and in fact, a stripping agent such as hydrogen sulfide is necessary. Use of hydrogen sulfide has the disadvantage of producing a precipitate with poor handling properties, of introducing sulfide ions into the leach solution, and yielding an impure sulfide precipitate which must be further refined.